Different colors for each holiday

Can I shade different holidays in different colors, for example company holidays in one color and plant closures in another?

Yes. Starting with version 2025, each holiday can have its own shade color.

On the Dates tab, choose Date Range Tools | Holidays (schedule) or Holidays (global).
Click each holiday. Use the scroll bar on the right to move forward and backward in time.
Click the small color box in the corner of a date to choose that holiday's color.
On the Dates tab, choose Weekly, Daily and Holiday Shading and check Shade Holidays.

Holidays shaded in different colors

Horizontal gridlines can also be shown over holiday and weekend shading.